A device of this type is disclosed by German Auslegeschrift No. 1,931,012. In this device, the holding element is provided with a slotted annular clamp having approximately radially projecting flanges in the vicinity of the slot. The lengthwise adjustable gas spring serving as a column, whose use as a chair column, table column, or the like, is there described in detail and which is hereby incorporated by reference, is inserted from below into the recess of the clamp. Then the clamp is tensioned to clamp the column in place by a tensioning screw that squeezes together the two flanges, and therefore the clamp, firmly against the outer circumference of the gas spring.
A device of this kind is extraordinarily simple and very reliable as long as the holding element can be made of steel, i.e., a material with some elasticity; hence, in order to replace the gas spring that serves as a column, it is necessary as a rule to bend the gas spring in order to pull it out after the tensioning screw has been loosened. If the holding element has a more complicated shape, because for example it must accept additional parts for a tipping device for a seat bottom, this holding element can no longer be made economically from steel, but must be made of die-cast or injection-molded metal, which has the disadvantage of being very inelastic and brittle. If in such cases the clamp should be bent, being made in one piece with the holding element, it would break.
In addition, it is known from German Utility Model No. 7,019,918 that the gas spring which serves as a column can be made conical in its upper area and the recess in the holding element can likewise be made conical. The connection between the gas spring and the holding element is then simply effected by pressing the holding element tightly against the gas spring. The clamping forces on the cone then suffice to keep it in place. This type of releasable fastening has the disadvantage, however, that slight differences in the diameter of the cone can lead to considerable differences in length when sliding it into the recess in the holding element and, under certain conditions, can cause problems with the actuation of the release rod of the gas spring. In addition, these conical connections are extraordinarily sensitive to tolerances and for these reasons are relatively costly to manufacture.
Furthermore, it is known that gas springs can be attached by means of a threaded connection to holding element fastenable to the seat bottom. In practice it has been found that if the two threaded parts are not applied with the correct torque, the connection will loosen, leading to wobbling of the seat bottom and consequent damage to the column, i.e. the gas spring.